Plate fin heat exchangers of the so-called drawn cup type which can be manufactured with a high efficiency are generally used as heat exchangers for use as air-cooled oil coolers or air-cooled after coolers for various industrial devices. The heat exchangers of this type comprise fluid channel members and fins which are arranged alternately in layers, the channel members being each composed of a pair of dishlike plates which are joined as opposed to each other. Each of the plates has at each of its opposite ends a header recessed portion which is shaped in the form of a cup by drawing and formed with a fluid passing hole in its bottom wall. The holes thus formed in the fluid channel members provide a header at each end of the heat exchanger.
In the case of the heat exchangers described, however, the plates are shaped by press work using a single kind of die, so that there arises a need to prepare another die anew when the length of the core portions, i.e., the length of the plates, is to be changed. Especially in the case of heat exchangers for industrial devices or apparatus which exchangers are fabricated in many kinds in a small quantity for each kind, it has been difficult to prepare plates of different lengths to meet the demands in view of the production cost of different dies.
In the case of the plate fin heat exchanger of the drawn cup type described, the cup-shaped header recessed portions of the plates have a reduced thickness smaller than the plate thickness owing to the drawing work, with the result that the headers become insufficient in pressure resistance, vibration resistance and corrosion resistance.
Conventional heat exchangers include those which comprise fluid channel members each formed by joining a pair of dishlike plates, or a dishlike plate and a flat plate, and annular header members each interposed between the corresponding ends of each pair of adjacent fluid channel members.
With such heat exchangers, the header members are superior to the header recessed portions of the plate fin heat exchanger of the drawn cup type in resistance to pressure, vibration and corrosion, whereas since the dishlike plates are similarly shaped by press work using a single kind of die, there arises a need to prepare another die anew when the length of the core portions, i.e., the length of the plates, is to be changed.
Heat exchangers are also available conventionally which comprise fluid channel members each composed of an intermediate plate having a channel forming slit and flat outer plates joined respectively to opposite sides of the intermediate plate, and annular header members each interposed between the corresponding ends of each pair of adjacent fluid channel members.
The heat exchangers of this type are inferior to plate fin heat exchangers of the drawn cup type in productivity, while there is a need to prepare another die anew when the length of the intermediate plates is to be changed. Additionally, if it is attempted to form a piping socket communication bore across two adjacent header members, for example, for connection to piping of increased diameter, the fluid channel member comprising three plates and having a relatively large thickness will offer resistance to the flow of fluid through the socket communication bore. It is therefore impossible to form the piping socket communication bore, consequently limiting the freedom to position the piping connection correspondingly.
An object of the present invention is to provide a heat exchanger which readily permits changes in the length of its core portions as demanded although comparable to plate fin heat exchangers of the drawn cup type in productivity and which comprises headers having high resistance to pressure, vibration and corrosion and is less likely to be limited in the freedom to position the piping connection.